mfussenegger / hprofdap

CLI and debug adapter (DAP) that allows to inspect Java heap dumps (.hprof files) via OQL

hprofdap

CLI and debug adapter (DAP) that allows to inspect Java heap dumps (.hprof files) via OQL

See a demo

Build

Requires Java 22

mvn package

DAP Installation/Configuration

hprofdap communicates via stdio.

Configure a debug-adapter client to spawn:

java \
    -Dpolyglot.engine.WarnInterpreterOnly=false \
    -jar path/to/repo/target/hprofdap-0.1.0-jar-with-dependencies.jar

Currently only the launch type is supported with one additional configuration property: filepath, which is expected to be a absolute path to the .hprof file you want to analyze.

nvim-dap example

dap.adapters.hprof = {
  type = "executable",
  command = os.getenv("JDK22") .. "/bin/java", -- or just "java"
  args = {
    "-Dpolyglot.engine.WarnInterpreterOnly=false",
    "-jar",
    vim.fn.expand("~/path/to/hprofdap/target/hprofdap-1.0-jar-with-dependencies.jar"),
  }
}
dap.configurations.java = {
  {
    name = "hprof",
    request = "launch",
    type = "hprof",
    filepath = function()
      return require("dap.utils").pick_file({
        executables = false,
        filter = "%.hprof$"
      })
    end,
  },
}

Usage

A .hprof file cannot be executed, therefore most of the functionality available during a regular debug session won't work. There are no breakpoints to hit, no stopped events, or anything like that.

Instead you can query the heap dump via OQL via the debug adapter's client's evaluate functionality.

Some examples of OQL queries:

select file from java.io.File file

select file.path from java.io.File file

select s from int[] s where s.length > 4000

Development

Debugging

Start hprofdap with jdwp enabled and use the bundled .vscode/launch.json attach configuration

-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005